536 ARM GLAND OF HAPAL&MUR CHAP. detail it may be stated generally that the anatomy of the brain of this group confirms the classification which is adopted in this work. A curious feature in the anatomy of the Lemurs, which they share with animals so remote from them in the system as the Edentata, is the breaking up of some of the arteries of the limbs to form retia mirabilia ; nothing of the kind is known among the other Primates. Perhaps the most remarkable difference between the Lemurs and the Anthropoidea, which are really in many respects more closely allied than might be inferred from the above summary of differences, is in the structure of the placenta. The Lemurs agree with the Ungulates in having a non-deciduate placenta. A curious feature confined to the sub-family Lemurinae was first discovered by myself in Hapalemur ffriseus* On the forearm (see Mg. 258) is an area of hardened skin, which, is raised into spine-like processes, Fully developed, this organ is characteristic of the male, the area being marked off in the female, but without the spiny outgrowths. On removing the skin a gland about the size and shape of an almond is brought into view. In other Lemurs there is no modified skin, but a small tuft of particularly long hairs, which are also present in Hapalemur, and a small gland beneath the skin. The gland of Scupaleinur may be comparable with a tract of hardened skin in L&m/wr catta, which projects to a large extent and has been spoken of as a " climbing organ." An almost exactly similar tuft of spine-like outgrowths exists upon the lower end of the ankle of Galago gwrnetti. The spines are black and bent, just as they are in JETa$dl&mur. There appears also to be a gland. This structure is not universal in the genus Grcdago any more than is the patch of spines in the genus Hapalemur. In addition to this gland and to the patch of spines which cover It, the same Lemur as well as Chirogaleus and certain species of Lemur possess to the inner side of it a bundle of long and stiff "bristles associated with unusually large sebaceous glands ; these structures are, of course, not homologous with the gland of the arm of Ifapaleffiur^ as they coexist in the same 1 ** On some Points in the Structure of JSapatemur griseus " Proc. Zool. Soe. 1884, p. 301.